Use of trypsin and lipoamidase to study the role of lipoic acid moieties in the pyruvate and .alpha.-ketoglutarate dehydrogenase complexes of Escherichia coli

The relationships between release of (3)H-labeled lipoyl moieties by trypsin and lipoamidase and accompanying loss of overall enzymatic activity of the Escherichia coli pyruvate and alpha-ketoglutarate dehydrogenase complexes were studied. Trypsin releases lipoyl domains together with their covalent...

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Bibliographic Details
Published in:Biochemistry (Easton) 1981-08, Vol.20 (16), p.4555-4560
Main Authors: Stepp, Larry R, Bleile, Dennis M, McRorie, Donald K, Pettit, Flora H, Reed, Lester J
Format: Article
Language:English
Subjects:
Amidohydrolases - metabolism
Binding Sites
enzymatic activity
Escherichia coli
Escherichia coli - enzymology
Ketoglutarate Dehydrogenase Complex - metabolism
Ketone Oxidoreductases - metabolism
Kinetics
lipoic acid
oxoglutarate dehydrogenase
pyruvate dehydrogenase
Pyruvate Dehydrogenase Complex - metabolism
Thioctic Acid - metabolism
Trypsin - metabolism
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Summary:The relationships between release of (3)H-labeled lipoyl moieties by trypsin and lipoamidase and accompanying loss of overall enzymatic activity of the Escherichia coli pyruvate and alpha-ketoglutarate dehydrogenase complexes were studied. Trypsin releases lipoyl domains together with their covalently attached lipoyl moieties from the "inner" core of the dihydrolipoyl transacetylase and the dihydrolipoyl transsuccinylase whereas lipoamidase releases only the lipoyl moieties. The results show that release of lipoyl domains by trypsin and release of lipoyl moieties by lipoamidase proceeded at faster rates than the accompanying loss of overall activity of the two complexes. Trypsin released about half of the lipoyl domains in the pyruvate dehydrogenase complex without significant effect on the overall activity. A model is presented to explain these and other observations on active-site coupling via lipoyl moieties.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00519a007